I think this card is actually much better for certain combo shenanigans than play dead would be (for rogue) and here's my logic:

you have a deathrattle you want to trigger four times:

with HUNTER, you can do this with 4 cards, that use up 6 mana, and take up 2 extra spaces on the board

with ROGUE, you can still do this with 4 cards, but only use up 4 mana, and not waste any board space (assuming you need it for cube shenanigans)

obviously the benefits of this card don't shine through in every situation, but in ones where 2 mana could make or break a combo (that needs 4 triggers) i think this is a significant improvement over what hunter has had access to.

Mechanical Whelp: 11 mana, 2 card combo, but it allows you to get 5 mana 14/14 worth of stats. To get this to work, however, you need either a Coin, Prep, or for your Whelp to stay on the board for one turn and NOT die.

Ultimately, it just doesn't seem like 5 mana for 2 Deathrattle pops isn't worth it just yet. That said, I am looking forward to that one time where some guy goes Mechanical Whelp --> Preparation --> Necrium Vial --> Prep --> Necrium Vial for the 10 mana 30/30 worth of stats.

One way to make the meme more reliable is if you Whelp --> Master of Disguise the Whelp so it has Stealth. Now they can't target the whelp, so it's much harder for them to kill it... unless they want to spend a board clear just to kill a 2/2.